Water dispersible polymer for use in additive manufacturing

ABSTRACT

A water dispersible sulfopolymer for use as a material in the layer-wise additive manufacture of a 3D part made of a non water dispersible polymer wherein the water dispersible polymer is a reaction product of a metal sulfo monomer, the water dispersible sulfo-polymer being dispersible in water resulting in separation of the water dispersible polymer from the 3D part made of the non water dispersible polymer.

BACKGROUND

The present disclosure relates to additive manufacturing systems forprinting three-dimensional (3D) parts and support structures. Inparticular, the present disclosure relates to support and buildmaterials for use in additive manufacturing systems, and methods ofusing the support and build materials as consumables in additivemanufacturing systems to print printed items.

Additive manufacturing is generally a process in which athree-dimensional (3D) object is manufactured utilizing a computer modelof the objects. The basic operation of an additive manufacturing systemconsists of slicing a three-dimensional computer model into thin crosssections, translating the result into two-dimensional position data, andfeeding the data to control equipment which manufacture athree-dimensional structure in a layerwise manner using one or moreadditive manufacturing techniques. Additive manufacturing entails manydifferent approaches to the method of fabrication, including fuseddeposition modeling, ink jetting, selective laser sintering,powder/binder jetting, electron-beam melting, electrophotographicimaging, and stereolithographic processes. In a fused depositionmodeling additive manufacturing system, a 3D part of model may beprinted from a digital representation of the 3D part in a layer-by-layermanner by extruding a flowable part material along toolpaths. The partmaterial is extruded through an extrusion tip carried by a print head ofthe system, and is deposited as a sequence of roads on a substrate in anx-y plane. The extruded part material fuses to previously deposited partmaterial, and solidifies upon a drop in temperature. The position of theprint head relative to the substrate is then incremented along a z-axis(perpendicular to the x-y plane) after each layer is formed, and theprocess is then repeated to form a printed item resembling the digitalrepresentation.

In an electrophotographic 3D printing process, each slice of the digitalrepresentation of the 3D part and its support structure is printed ordeveloped using an electrophotographic engine. The electrophotographicengine generally operates in accordance with 2D electrophotographicprinting processes, but with a polymeric toner. The electrophotographicengine typically uses a conductive support drum that is coated with aphotoconductive material layer, where latent electrostatic images areformed by electrostatic charging, followed by image-wise exposure of thephotoconductive layer by an optical source. The latent electrostaticimages are then moved to a developing station where the polymeric toneris applied to charged areas, or alternatively to discharged areas of thephotoconductive insulator to form the layer of the polymeric tonerrepresenting a slice of the 3D part. The developed layer is transferredto a transfer medium, from which the layer is transfused to previouslyprinted layers with heat and/or pressure to build the 3D part.

In fabricating printed items by depositing layers of a part material,supporting layers or structures are typically built underneathoverhanging portions or in cavities of printed items under construction,which are not supported by the part material itself. A support structuremay be built utilizing the same deposition techniques by which the partmaterial is deposited. A host computer generates additional geometryacting as a support structure for the overhanging or free-space segmentsof the 3D part being formed. The support material adheres to the partmaterial during fabrication, and is removable from the completed printeditem when the printing process is complete. Prior art methods ofremoving support structure have included simply breaking the supportstructure off of the part material and then smoothing out any residualrough areas, or dissolving away soluble supports using a water-basedsolution. It is desirable to have a support structure that can beremoved without special tool or solutions, and with minimal labor. Amore easily removable support structure reduces time of manufacture ofthe part in addition to making the process of removing the supportstructure easier.

SUMMARY

A water dispersible sulfopolymer for use as a sacrificial supportmaterial in the layer-wise additive manufacture of a printed part madeof a non water dispersible polymer, wherein the water dispersiblepolymer is a reaction product of a sulfo monomer, the water dispersiblesulfopolymer being dispersible in water resulting in separation of thewater dispersible polymer from the part made of the non waterdispersible polymer.

In another aspect, a water dispersible sulfopolymer is supplied as asacrificial support material in the layer-wise additive manufacture of aprinted part made of a non water dispersible polymer. The waterdispersible polymer has a heat deflection temperature within ±20° C. ofthe heat deflection temperature of the non water dispersible polymer orpreferably within ±15° C. of the heat deflection temperature of the nonwater dispersible polymer, wherein the water dispersible polymer is areaction product of a sulfo monomer, the water dispersible sulfopolymerbeing dispersible in water resulting in separation of the waterdispersible polymer from the part made of the non water dispersiblepolymer.

In another aspect, a water dispersible sulfopolymer is supplied as asacrificial support material in the layer-wise additive manufacture of aprinted part made of a non water dispersible polymer. The waterdispersible polymer has a glass transition temperature within ±20° C. ofthe glass transition temperature of the non water dispersible polymer orpreferably within ±15° C. of the glass transition temperature of the nonwater dispersible polymer, wherein the water dispersible polymer is areaction product of a metal sulfo monomer, the water dispersiblesulfopolymer being dispersible in water resulting in separation of thewater dispersible polymer from the part comprising the non waterdispersible polymer.

In another aspect, the water dispersible sulfopolymer is a reactionproduct of a metal sulfo-monomer.

In yet another aspect of this disclosure, the water dispersiblesulfopolymer has a charge density of at least approximately 0.4 meq./g,such that the water dispersible sulfopolymer is dispersible in waterresulting in separation of the water dispersible sulfopolymer from thepart comprising the non water dispersible polymer.

In a further aspect of this disclosure, the water dispersiblesulfopolymer is used in a method of manufacturing a sacrificial supportstructure for use with a 3D printed part made of the non waterdispersible polymer. The method of manufacturing comprises printing thesupport structure as a series of successive layers of the waterdispersible sulfopolymer, the water dispersible sulfopolymer having aglass transition temperature wherein the water dispersible polymer has aglass transition temperature within ±20° C. of the glass transitiontemperature of the non water dispersible polymer or preferably within±15° C. of the glass transition temperature of the non water dispersiblepolymer, wherein the water dispersible polymer is a reaction product ofa sulfo monomer, and separating the non water dispersible polymer fromthe water dispersible sulfopolymer by subjecting the water dispersiblesulfopolymer to water.

In a further aspect of this disclosure, the water dispersiblesulfopolymer is used in a method of manufacturing a sacrificial supportstructure for use with a part made of the non water dispersible polymer.The method of manufacturing comprises printing the support structure asa series of successive layers with the water dispersible sulfopolymer,the water dispersible sulfopolymer having a heat deflection temperaturewherein the water dispersible polymer has a heat deflection temperaturewithin ±20° C. of the heat deflection temperature of the non waterdispersible polymer or preferably within ±15° C. of the heat deflectiontemperature of the non water dispersible polymer, wherein the waterdispersible polymer is a reaction product of a sulfo monomer, andseparating the non water dispersible polymer from the water dispersiblesulfopolymer by subjecting the water dispersible sulfopolymer to water.

In another aspect of this disclosure the water dispersible sulfopolymerpreferably has approximately 18 to 40% metal sulfoisophthalic monomer,with a more preferred range of approximately 20 to 35% metalsulfoisophthalic monomer and most preferably approximately 25 to 35%metal sulfoisophthalic monomer.

In a further aspect, the water dispersible polymer of this disclosure isa sulfopolymer which is also substantially amorphous.

Definitions

Unless otherwise specified, the following terms as used herein have themeanings provided below:

The term “polymer” refers to a polymerized molecule having one or moremonomer species, and includes homopolymers and copolymers. The term“copolymer” refers to a polymer having two or more monomer species, andincludes terpolymers (i.e., copolymers having three monomer species).

The terms “preferred” and “preferably” refer to embodiments that mayafford certain benefits, under certain circumstances. However, otherembodiments may also be preferred, under the same or othercircumstances. Furthermore, the recitation of one or more preferredembodiments does not imply that other embodiments are not useful, and isnot intended to exclude other embodiments from the inventive scope ofthe present disclosure.

Reference to “a” chemical compound refers to one or more molecules ofthe chemical compound, rather than being limited to a single molecule ofthe chemical compound. Furthermore, the one or more molecules may or maynot be identical, so long as they fall under the category of thechemical compound. Thus, for example, “a” polyester is interpreted toinclude one or more polymer molecules of the polyester, where thepolymer molecules may or may not be identical (e.g., different molecularweights and/or isomers).

The terms “at least one” and “one or more of” an element are usedinterchangeably, and have the same meaning that includes a singleelement and a plurality of the elements, and may also be represented bythe suffix “(s)” at the end of the element. For example, “at least onepolyester”, “one or more polyesters”, and “polyester(s)” may be usedinterchangeably and have the same meaning.

The terms “about”, approximately and “substantially” are used hereinwith respect to measurable values and ranges due to expected variationsknown to those skilled in the art (e.g., limitations and variability inmeasurements).

The term “providing”, such as when recited in the claims, is notintended to require any particular delivery or receipt of the provideditem. Rather, the term “providing” is merely used to recite items thatwill be referred to in subsequent elements of the claim(s), for purposesof clarity and ease of readability.

Unless otherwise specified, temperatures referred to herein are based onatmospheric pressure (i.e. one atmosphere).

“Soluble” as referred to herein can be used interchangeably with“disintegrable” and “dissolvable” and relates to materials thatdisintegrate in a solution or dispersion. Upon disintegration, the waterdispersible material can break apart into smaller pieces and/orparticles of polymer in the solution or dispersion. Some or all of thewater dispersible material may also dissolve into the solution ordispersion upon disintegration.

“Water soluble” as used herein relates to materials that dissolve in tapwater that is about neutral pH. It is understood that the pH of tapwater can vary depending on the municipality and as such the pH can varybetween about 5 and about 9. Although these pH's are slightly basic orslightly acidic, the defining feature of the water soluble materials isthat they do not require an acidic or basic solution to disintegrate andcan disintegrate in water at about neutral pH, e.g. tap water.

“High temperature build environment” as referred to herein relates tobuild environments of about 45° C. or greater in additive manufacturingsystems.

“Heat deflection temperature” or “heat distortion temperature” (HDT) isthe temperature at which a polymer sample deforms under a specified loadand is determined by the test procedure outlined in ASTM D648.

“Thermally stable” as referred to herein relates to the material havinga heat deflection temperature sometimes referred to as heat distortiontemperature (HDT) compatible with the desired build environment suchthat they do not exceed their thermal-degradation kinetics thresholds.

The term “polyester” referred to herein relates to a polymer thatcontains an ester functional group in its main chain. As used herein,the term “sulfopolyester” means any polyester that contains asulfomonomer.

The term “polyamide” referred to herein relates to both aliphatic andaromatic polyamides. In the case of an aliphatic polyamide such as nylon6 and nylon 66, the amide link is produced from the condensationreaction of an amino group and a carboxylic acid group wherein water iseliminated. For aromatic polyamides or ‘aramids’ such as Kevlar, an acidchloride is used as a monomer. As used herein, the term “sulfopolyamide”means any polyamide that contains a sulfomonomer.

The term “polyurethane” referred to herein relates to polymers that aremost commonly formed by reacting a di- or polyisocyanate with a polyol.As used herein, the term “sulfopolyurethane” means any polyurethane thatcontains a sulfomonomer.

The term “polyesteramide” referred to herein relates to polymers thatcontain an ester and an amide functional group in its main chain. Forexample, it can be achieved by combining a di-acid and a diol with adiamine, or a hydroxycarboxylic acid and an amine, or an aminocarboxylicacid and a diol. As used herein, the term “Sulfopolyesteramide means anypolyesteramide that contains a sulfomonomer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of an extrusion-based additive manufacturingsystem configured to print printed parts and support structures, wherethe support structures are printed from a water dispersible material ofthe present disclosure.

FIG. 2 is a front view of a print head of the extrusion-based additivemanufacturing system.

FIG. 3 is an expanded sectional view of a drive mechanism, a liquefierassembly, and a nozzle of the print head for use in the extrusion-basedadditive manufacturing system.

FIG. 4 is a simplified diagram of an exemplary electrophotography-basedadditive manufacturing system for printing 3D parts and associatedsupport structures, in accordance with embodiments of the presentdisclosure.

FIG. 5 is a schematic front view of a pair of exemplaryelectrophotography engines of the system for developing layers of thepart and support materials.

FIG. 6 is a schematic front view of an exemplary electrophotographyengine, which includes an intermediary drum or belt.

FIG. 7 is a schematic front view of an exemplary transfusion assembly ofthe system for performing layer transfusion steps with the developedlayers.

DETAILED DESCRIPTION

The present disclosure is directed to a water dispersible sulfopolymermaterial for use in 3D printing. The sulfopolymer material can be usedfor printing sacrificial support structures for 3D parts built in arange of build temperature environments of additive manufacturingsystems. It can also be used for layer-wise printing of dissolvable 3Dparts.

The water dispersible material of the present disclosure functions as asacrificial material for an associated part material in additivemanufacturing (aka 3D printing) applications. A sacrificial supportmaterial can be desirable where overhanging features are required, wheresignificant angular slopes exist in the printed items and where it isessential to also preserve delicate features in the printed item, suchas small orifices or controlled pore structures, and in some situations,to laterally encase the printed item. Once the item has been printed,the support structure of the water dispersible material is removed toreveal the completed printed item without damaging any of the criticalor delicate geometrical features of the printed item. To accomplish thisremoval, the disclosed material is water dispersible, allowing thesupport structure to be at least partially and typically completelydissolved away from the printed item. The support structure made be madesolely of the water dispersible polymer of this disclosure or othernon-dispersible polymers may be incorporated therein as long as thewater dispersibility is not substantially affected. In addition mixturesof other sulfopolymers, water-soluble polymers, and non-solublepolymers; additives, fillers, and/or stabilizers may be added to thewater dispersible polymer.

The present disclosure also includes the use of the water dispersiblepolymer for manufacturing a dissolvable part suitable for downstreamuses such as sacrificial tooling. A sacrificial tool encompassing thewater dispersible polymer may be a dissolvable core type structure onwhich a part or device is subsequently produced or providing some typeof platform for subsequent manufacture of a part or device. Such aprocess is distinguished from for example a direct additivemanufacturing process wherein both the part and the support structureare concurrently printed. For example a device made of carbon fibers maybe formed around the sacrificial tooling made of the water dispersiblepolymer. Once the carbon fiber device is made, the water dispersiblepolymer is disintegrated by introducing the water dispersible polymer towater.

The water used to disperse the water dispersible polymer is plain tap ornaturally occurring water. Support removal does not require the presenceof a basic or acidic environment or heating of the aqueous solution. Inaddition, the solubility of the water dispersible material is sufficientfor use of removal of the supports in an automated process or hands-freemanner Plain tap water typically has an average pH of approximately 7.However, water pH varies greatly, ranging anywhere from having a pHbetween approximately 5.0 and 9 is also suitable. In any event, the pHof the water does not need to be adjusted to disintegrate the waterdispersible polymer. After it disintegrates, the dispersed water solublepolymer solution may be processed by increasing the ionic strength ofthe solution to precipitate out the water dispersible polymer. The water(with the water soluble polymer removed) may then be recycled for reuseto remove the water dispersible polymer from subsequent parts.

In the embodiment of additive manufacturing, in order to effectivelyprint a support structure in a layer-by-layer manner in coordinationwith a printed item for example in a fused deposition modeling process,amorphous support materials preferably have a glass transitiontemperature that is approximately equivalent to or higher than the Tg ofthe part material. For example a Tg of ±20 C with a more preferred rangeof ±15 C of the support material with respect to the Tg of the partmaterial would be considered approximately equivalent. This allows thepart and support materials to have similar heat deflection temperaturesand other thermal characteristics when printed together as a materialpair. For example, similar glass transition and heat deflectiontemperatures allow the part and support materials to be printed togetherin the same heated environment while preventing excessive distortionsand curling. For semi-crystalline or crystalline support materials, heatdeflection temperature is more indicative of acceptable performance thanTg pairing of part and support materials. Semi-crystalline orcrystalline support materials are more suitable for particulate additivemanufacturing such as selective laser sintering, or electrophotographicimaging. An example of suitably equivalent heat deflection temperaturesare ±20° C. with a more preferred range of ±15° C.

The water dispersible material of the present disclosure may beconfigured for use with several different additive manufacturingtechniques, such as extrusion-based additive manufacturing systems,high-speed sintering systems, selective laser sintering systems,electrophotography-based additive manufacturing systems, and the like.

Depending on the additive manufacturing technique selected, it may bedesired to customize the level of crystallinity of the polymericmaterial. For example, in SLS or other sintering applications,crystallinity is desired. In FDM applications, it is more desirable touse amorphous polymeric materials. The level of crystallinity can bemanipulated during manufacture of the material via monomer selection.

As shown in FIG. 1, system 10 is an example of an extrusion-basedadditive manufacturing system for printing or otherwise building 3Dparts and support structures using a layer-based, additive manufacturingtechnique, where the support structures may be printed from the waterdispersible material of the present disclosure. Suitable extrusion-basedadditive manufacturing systems for system 10 include fused depositionmodeling systems developed by Stratasys, Inc., Eden Prairie, Minn. underthe trademark “FDM”.

In the illustrated embodiment, system 10 includes chamber 12, platen 14,platen gantry 16, print head 18, head gantry 20, and consumableassemblies 22 and 24. Chamber 12 is an enclosed environment thatcontains platen 14 for printing printed parts and support structures.Chamber 12 may be heated (e.g., with circulating heated air) to reducethe rate at which the part and support materials solidify after beingextruded and deposited.

Alternatively, the heating may be localized rather than in an entirechamber 12. For example, the deposition region may be heated in alocalized manner Example techniques for locally heating a depositionregion include heating platen 14 and/or with directing heat air jetstowards platen 14 and/or the printed parts/support structures beingprinted). The heating anneals the printed layers of the printed parts(and support structures) to partially relieve the residual stresses,thereby reducing curling of the printed parts and support structures.

Platen 14 is a platform on which printed parts and support structuresare printed in a layer-by-layer manner. In some embodiments, platen 14may also include a flexible polymeric film or liner on which the printedparts and support structures are printed. In the shown example, printhead 18 is a dual-tip extrusion head configured to receive consumablefilaments from consumable assemblies 22 and 24 (e.g., via guide tubes 26and 28) for printing printed part 30 and support structure 32 on platen14. Consumable assembly 22 may contain a supply of a part material, suchas a high-performance part material, for printing printed part 30 fromthe part material. Consumable assembly 24 may contain a supply of asupport material of the present disclosure for printing supportstructure 32 from the given support material.

Platen 14 is supported by platen gantry 16, which is a gantry assemblyconfigured to move platen 14 along (or substantially along) a verticalz-axis. Correspondingly, print head 18 is supported by head gantry 20,which is a gantry assembly configured to move print head 18 in (orsubstantially in) a horizontal x-y plane above chamber 12.

In an alternative embodiment, platen 14 may be configured to move in thehorizontal x-y plane within chamber 12, and print head 18 may beconfigured to move along the z-axis. Other similar arrangements may alsobe used such that one or both of platen 14 and print head 18 aremoveable relative to each other. Platen 14 and print head 18 may also beoriented along different axes. For example, platen 14 may be orientedvertically and print head 18 may print printed part 30 and supportstructure 32 along the x-axis or the y-axis.

System 10 also includes controller 34, which is one or more controlcircuits configured to monitor and operate the components of system 10.For example, one or more of the control functions performed bycontroller 34 can be implemented in hardware, software, firmware, andthe like, or a combination thereof. Controller 34 may communicate overcommunication line 36 with chamber 12 (e.g., with a heating unit forchamber 12), print head 18, and various sensors, calibration devices,display devices, and/or user input devices.

System 12 and/or controller 34 may also communicate with computer 38,which is one or more computer-based systems that communicates withsystem 12 and/or controller 34, and may be separate from system 12, oralternatively may be an internal component of system 12. Computer 38includes computer-based hardware, such as data storage devices,processors, memory modules, and the like for generating and storing toolpath and related printing instructions. Computer 38 may transmit theseinstructions to system 10 (e.g., to controller 34) to perform printingoperations.

FIG. 2 illustrates a suitable dual-tip device for print head 18, asdescribed in Leavitt, U.S. Pat. No. 7,625,200. Additional examples ofsuitable devices for print head 18, and the connections between printhead 18 and head gantry 20 include those disclosed in Crump et al., U.S.Pat. No. 5,503,785; Swanson et al., U.S. Pat. No. 6,004,124; LaBossiere,et al., U.S. Pat. Nos. 7,384,255 and 7,604,470; Leavitt, U.S. Pat. No.7,625,200; Batchelder et al., U.S. Pat. No. 7,896,209; Comb et al., U.S.Pat. No. 8,153,182; and Swanson et al., U.S. Pat. Nos. 8,419,996 and8,647,102.

In the shown embodiment, print head 18 includes two drive mechanisms 40and 42, two liquefier assemblies 44 and 46, and two nozzles 48 and 50,where drive mechanism 40, liquefier assembly 44, and nozzle 48 are forreceiving and extruding the part material, and drive mechanism 42,liquefier assembly 46, and nozzle 50 are for receiving and extruding thesupport material of the present disclosure. In this embodiment the partmaterial and the support material each preferably have a filamentgeometry for use with print head 18. For example, as shown in FIGS. 2and 3, the support material may be provided as filament 52. Duringoperation, controller 34 may direct wheels 54 of drive mechanism 42 toselectively draw successive segments filament 52 (of the supportmaterial) from consumable assembly 24 (via guide tube 28), and feedfilament 52 to liquefier assembly 46. In alternative embodiments, theconsumable material may be provided in other geometries or formatsadapted for other types of print heads and feed systems, such as powder,liquid, pellet, slug, or ribbon forms.

Liquefier assembly 46 is heated to melt the provided consumable materialto form melt 70. Preferred liquefier temperatures will vary depending onthe particular polymer composition of the consumable material, and arepreferably above the melt processing temperature of the material. Themolten portion of the material (i.e., melt 70) forms meniscus 74 aroundthe unmelted portion of filament 52. During an extrusion of melt 70through nozzle 50, the downward movement of filament 52 functions as aviscosity pump to extrude the support material of melt 70 out of nozzle50 as extruded roads, to thereby print support structure 32 in alayer-by-layer manner in coordination with the printing of printed part30. After the print operation is complete, the resulting printed part 30and support structure 32 may be removed from chamber 12. Supportstructure 32 may then be sacrificially removed from printed part 30,such as by dissolution in tap water.

The compositions of the present invention may also be provided in powderform for use in additive manufacturing systems that use powder-basedconsumables, e.g., electrophotography-based additive manufacturingsystems and selective laser sintering systems. Electrophotography-basedadditive manufacturing systems are disclosed, for example, in Hanson etal., U.S. Publication Nos. 2013/0077996 and 2013/0077997, and Comb etal., U.S. Publication Nos. 2013/0186549 and 2013/0186558. Powdermaterials for use in EP-based AM systems have a particle sizedistribution ranging from about 5 micrometers to about 30 micrometers,have a heat deflection temperature of up to about 150 deg. C., andinclude a charge control agent. The addition of a charge control agentto polymer powders for EP-based systems is disclosed in Orrock et al.,U.S. Publication No. 20150024316, the disclosure of which isincorporated by reference to the extent that it does not conflict withthe present disclosure.

In an exemplary electro-photography based additive manufacturing system,each layer or partial thickness layer may be developed usingelectrophotography and carried from an electrophotography (EP) engine bya transfer medium (e.g., a rotatable belt or drum). The layer or partialthickness layer includes part material, and optionally support material.The partial thickness layer is then transferred to a build platform toprint the 3D part (or support structure) in a layer-by-layer manner,where the successive partial thickness layers are transfused together toproduce the 3D part (or support structure). Printing with partialthickness layers increases the resolution of the 3D part in the zdirection relative to 3D parts printed with layers having the thicknessof the nominal thickness of the slice.

FIG. 4 is a simplified diagram of an exemplary electrophotography-basedadditive manufacturing system 110 for printing 3D parts and associatedsupport structures. As shown in FIG. 4, system 110 includes one or moreEP engines, generally referred to as 112, such as EP engines 112 p and112 s, a transfer assembly 114, biasing mechanisms 116, and atransfusion assembly 120. Examples of suitable components and functionaloperations for system 110 include those disclosed in Hanson et al., U.S.Pat. Nos. 8,879,957 and 8,488,994, and in Comb et al., U.S. Patents Nos.2013/0186549 and 2013/0186558.

The EP engines 112 p and 112 s are imaging engines for respectivelyimaging or otherwise developing layers, generally referred to as 122, ofthe powder-based part and support materials. As discussed below, thedeveloped layers 122 are transferred to a transfer medium 124 of thetransfer assembly 114, which delivers the layers 122 to the transfusionassembly 120. The transfusion assembly 120 operates to build the 3D part126, which may include support structures and other features, in alayer-by-layer manner by transfusing the layers 122 together on a buildsubstrate 128.

The transfer assembly 114 includes one or more drive mechanisms thatinclude, for example, a motor 130 and a drive roller 133, or othersuitable drive mechanism, and operate to drive a transfer medium or belt124 in a feed direction 132. The transfer assembly 114 includes idlerrollers 134 that provide support for the belt 124. The EP engine 112 sdevelops layers of powder-based support material, and the EP engine 112p develops layers of powder-based part material.

System 110 also includes controller 136, which represents one or moreprocessors that are configured to execute instructions, which may bestored in memory of the system 110 to control components of the system110 to perform one or more functions described herein.

The host computer 138 may include one or more computer-based systemsthat are configured to communicate with controller 136 to provide theprint instructions and other operating information.

FIG. 5 is a schematic front view of the EP engines 112 s and 112 p ofthe system 110. The EP engines 112 p and 112 s may include the samecomponents, such as a photoconductor drum 142 having a conductive drumbody 144 and a photoconductive surface 146 and configured to rotatearound a shaft 148. The shaft 148 is correspondingly connected to adrive motor 150, which is configured to rotate the shaft 148 (and thephotoconductor drum 142) in the direction of arrow 152 at a constantrate.

The surface 146 is configured to receive latent-charged images of thesliced layers of a 3D part or support structure (or negative images),and to attract charged particles of the part or support material to thecharged or discharged image areas, thereby creating the layers of the 3Dpart or support structure.

As further shown, each of the exemplary EP engines 112 p and 112 s alsoincludes a charge inducer 154, an imager 156, a development station 158,a cleaning station 160, and a discharge device 162, each of which may bein signal communication with the controller 136. The charge inducer 154,the imager 156, the development station 158, the cleaning station 160,and the discharge device 162 accordingly define an image-formingassembly for the surface 146 while the drive motor 150 and the shaft 148rotate the photoconductor drum 142 in the direction 152.

The EP engines 112 use the powder-based material generally referred toherein as 166, to develop or form the layers 122. The image-formingassembly for the surface 146 of the EP engine 112 s is used to formsupport layers 122 s of the powder-based support material 166 s, where asupply of the support material 166 s may be retained by the developmentstation 158 (of the EP engine 112 s) along with carrier particles.Similarly, the image-forming assembly for the surface 146 of the EPengine 112 p is used to form part layers 122 p of the powder-based partmaterial 166 p, where a supply of the part material 166 p may beretained by the development station 158 (of the EP engine 112 p) alongwith carrier particles.

The charge inducer 154 is configured to generate a uniform electrostaticcharge on the surface 146 as the surface 146 rotates in the direction152 past the charge inducer 154.

The imager 156 is a digitally-controlled, pixel-wise light exposureapparatus configured to selectively emit electromagnetic radiationtoward the uniform electrostatic charge on the surface 146 as thesurface 146 rotates in the direction 152 the part imager 156. Theselective exposure of the electromagnetic radiation to the surface 146is directed by the controller 36, and causes discrete pixel-wiselocations of the electrostatic charge to be removed (i.e., discharged toground), thereby forming latent image charge patterns on the surface146.

Suitable devices for the imager 156 include scanning laser (e.g., gas orsolid state lasers) light sources, light emitting diode (LED) arrayexposure devices, and other exposure device conventionally used in 2Delectrophotography systems. In alternative embodiments, suitable devicesfor the charge inducer 154 and the imager 156 include ion-depositionsystems configured to selectively directly deposit charged ions orelectrons to the surface 46 to form the latent image charge pattern.

Each development station 158 is an electrostatic and magneticdevelopment station or cartridge that retains the supply of the partmaterial 166 p or the support material 166 s, along with carrierparticles. When agitated, the carrier particles generate triboelectriccharges to attract the powders of the part material 166 p or the supportmaterial 166 s, which charges the attracted powders to a desired signand magnitude, as discussed below.

Each development station 158 may also include one or more devices fortransferring the charged part or the support material 166 p or 166 s tothe surface 146, such as conveyors, fur brushes, paddle wheels, rollers,and/or magnetic brushes. The photoconductor drum 112 rotates in thedirection 152, where successive layers 122 p or 122 s correspond to thesuccessive sliced layers of the digital representation of the 3D part orsupport structure. The successive layers 122 p or 122 s are then rotatedwith the surface 146 in the direction 152 to a transfer region in whichlayers 122 p or 122 s are successively transferred from thephotoconductor drum 142 to the belt 124 or other transfer medium.

After a given layer 122 p or 122 s is transferred from thephotoconductor drum 142 to the belt 124 (or an intermediary transferdrum or belt), the drive motor 150 and the shaft 148 continue to rotatethe photoconductor drum 142 in the direction 152 such that the region ofthe surface 146 that previously held the layer 122 p or 122 s passes thecleaning station 160.

After passing the cleaning station 160, the surface 146 continues torotate in the direction 152 such that the cleaned regions of the surface146 past the discharge device 162 to remove any residual electrostaticcharge on the surface 146, prior to starting the next cycle.

The biasing mechanisms 116 are configured to induce electricalpotentials through the belt 124 to electrostatically attract the layers122 p and 122 s from the EP engines 112 p and 112 s to the belt 124.Because the layers 122 p and 122 s are each only a single layerincrement in thickness at this point in the process, electrostaticattraction is suitable for transferring the layers 122 p and 122 s fromthe EP engines 112 p and 112 s to the belt 124.

The controller 136 preferably rotates the photoconductor drums 136 ofthe EP engines 112 p and 112 s at the same rotational rates that aresynchronized with the line speed of the belt 124 and/or with anyintermediary transfer drums or belts. This allows the system 110 todevelop and transfer the layers 122 p and 122 s in coordination witheach other from separate developer images. In particular, as shown, eachpart layer 122 p may be transferred to the belt 124 with properregistration with each support layer 122 s to produce a combined partand support material layer, which is generally designated as layer 122.As can be appreciated, some of the layers 122 transferred to the layertransfusion assembly 120 may only include support material 166 s or mayonly include part material 166 p, depending on the particular supportstructure and 3D part geometries and layer slicing.

FIG. 7 illustrates the transfusion assembly 120 which includes the buildplatform 128, a nip roller 170, pre-transfusion heaters 172 and 174, anoptional post-transfusion heater 176, and air jets 178. The buildplatform 128 is configured to receive the heated combined layers 122 (orseparate layers 122 p and 122 s) for printing the part 126, whichincludes a 3D part 126 p formed of the part layers 122 p, and supportstructure 126 s formed of the support layers 122 s, in a layer-by-layermanner.

The build substrate 128 is supported by a gantry 184 or other suitablemechanism, which is configured to move the build platform 128 along thez-axis and the x-axis, as illustrated schematically in FIG. 4. Thegantry 184 may be operated by a motor 188 based on commands from thecontroller 136.

The build substrate 128 is heatable with heating element 190 configuredto heat and maintain the build platform 128 at an elevated temperaturethat is greater than room temperature (25° C.), such as at a desiredaverage part temperature of 3D part 126 p and/or support structure 126s, as discussed in Comb et al., U.S. Patent Application Publication Nos.2013/0186549 and 2013/0186558. This allows the build platform 128 toassist in maintaining 3D part 126 p and/or support structure 26 s atthis average part temperature.

The nip roller 170 is an exemplary heatable element or heatable layertransfusion element, which is configured to rotate around a fixed axiswith the movement of the belt 124. The heating element 194 is configuredto heat and maintain nip roller 170 at an elevated temperature that isgreater than room temperature (25° C.), such as at a desired transfertemperature for the layers 122.

The pre-transfusion heater 172 includes one or more heating devices thatare configured to heat the layers 122 on the belt 124 to a temperaturenear an intended transfer temperature of the layer 122 prior to reachingnip roller 170. Each layer 122 desirably passes by (or through) theheater 172 for a sufficient residence time to heat the layer 122 to theintended transfer temperature. Optional post-transfusion heater 176 islocated downstream from nip roller 170 and upstream from air jets 178.

During the printing or transferring operation, the belt 124 carries alayer 122 past the heater 172, which may heat the layer 122 and theassociated region of the belt 124 to the transfer temperature. Suitabletransfer temperatures for the part and support materials 166 p and 166 sof the present disclosure include temperatures that exceed the glasstransition temperature of the part and support materials 166 p and 166s, where the layer 122 is softened but not melted.

As further shown in FIG. 7 the gantry 184 moves the build substrate 128(with 3D part 126 p and support structure 126 s) in a reciprocatingrectangular pattern 186. The heater 174 heats the top surfaces of 3Dpart 126 p and support structure 126 s to an elevated temperature. Asdiscussed in Comb et al., U.S. Patent Publication Nos. 2013/0186549 and2013/0186558, the heaters 172 and 174 may heat the layers 122 and thetop surfaces of 3D part 126 p and support structure 126 s to about thesame or different temperatures to provide a consistent transfusioninterface temperature.

The continued rotation of the belt 124 and the movement of the buildplatform 128 align the heated layer 122 with the heated top surfaces of3D part 126 p and support structure 126 s. The gantry 184 moves thebuild platform 128 along the x-axis, at a rate that is synchronized withthe rotational rate of the belt 124 in the feed direction 132.

As the transfused layer 122 passes the nip of the nip roller 170, thebelt 124 wraps around the nip roller 170 to separate and disengage fromthe build platform 128. This assists in releasing the transfused layer122 from the belt 124, allowing the transfused layer 122 to remainadhered to 3D part 126 p and support structure 126 s.

After release, the gantry 184 continues to move the build platform 128along the x-axis to the post-transfusion heater 176. At post-transfusionheater 176, the top-most layers of 3D part 126 p and the supportstructure 126 s (including the transfused layer 122) may then be heatedto at least the fusion temperature of the thermoplastic-based powder ina post-fuse or heat-setting step.

As mentioned above, the water dispersible material of the presentdisclosure compositionally comprises a sulfopolymer. It is believed thatan important characteristic of the sulfopolymers of this disclosure is“charge density”. Cationic and anionic polymers are characterized bytheir charge density. An anionic polymer is a polymer containing groupsreasonably anticipated to become anionic. Charge density is usuallyexpressed in milliequivalents (meq) of ionic groups per gram of polymer.Suitable charge densities for sulfopolyesters of this disclosure are inthe approximate range of (0.4 to 0.9 meq/g). Suitable charge densitiesare also those that for any particular sulfopolymer provide a waterdispersibility characteristic to that sulfopolymer. Sulfopolyesters withhigh charge densities are more easily and quickly dispersed in water,lending themselves to faster manufacturing removal. Lower chargedensities produce polymers that are resistant to water dispersibility.Higher charge density relating to better dispersibility in water isbelieved to be also a characteristic of other anionic polymers asanionic polymers are defined herein.

The use of a sodium or lithium salt of isophthalic acid such as5-sodiosulfoisophthalic acid (5-SSIPA) (CAS #6362-79-4) or derivativesthereof as a monomer in the synthesis of a sulfopolymer has been foundto be suitable as a consumable material for use in layer-wise additivemanufacturing. In addition, the inclusion of 5-SSIPA as a monomerprovides a suitable charge density to that polymer if added in an amountsufficient to provide water dispersibility. 5-SSIPA can be used as amonomer in producing condensation polymers including but not limited tosulfopolyesters, sulfopolyamides, sulfopolyesteramides,sulfopolyurethanes and blends thereof results in sulfopolymers thatexhibit water solubility and/or dispersibility. Sulfonation of otherpolymer categories such as polystyrene, polyvinyl acetate, polyvinylchloride, polyacrylates, polyvinylidine chloride, polyimides,polyarylsulfones, polycarbonates, including copolymers or admixturesthereof are also contemplated. The use of other sulfonated aromaticdiacid or diol monomers in the synthesis of a sulfopolymer iscontemplated to be useful as a water dispersible 3D printing materialwithin this disclosure. Preferably, the polymer contains approximately18 to 40% sulfoisophthalic monomer, with a more preferred range ofapproximately 20 to 35% sulfoisophthalic monomer and most preferablyapproximately 25 to 35% sulfoisophthalic monomer. Examples of thesulfoisophthalic monomer may include but are not limited tosodiosulfoisophthalic monomers.

Sulfo-Polyesters

Water dispersible sulfo-polyesters having a glass transition temperatureof greater than 100° C. can be prepared and are described in U.S. Pat.No. 5,369,210, which is hereby incorporated by reference in itsentirety. Sulfo-polyesters having a Tg in the approximate range of 105to 120 C are suitable support materials for ABS part material.

The sulfo-polyesters of this disclosure may have a dicarboxylic acidcomponent of poly(ethylene-2,6-naphthalene dicarboxylate and asulfo-monomer, and a diol component selected from ethylene glycol,diethylene glycol, 1,4-cyclohexanedimethanol, propane-1,2-diol and2,2-dimethyl-1,3-propanediol. The diol component may also includebisphenol A (BpA) and/or other diphenylmethane derivatives andbisphenols with two hydroxyphenyl groups to effect higher Tgs in thepolymer. Preferably, the sulfo-monomer is 5-sodiosulfoisophthalic acid(CAS #6362-79-4), or derivatives thereof. Other metallic sulfomonomersare additionally contemplated.

The sulfo-polyester contains repeat units from a dicarboxylic acid and adifunctional sulfomonomer, and a diol. Dicarboxylic acids useful in thepresent invention include naphthalene dicarboxylic acid or naphthalenedicarboxylate ester such as naphthalene-2,6-dicarboxylic acid. Thenaphthalene dicarboxylate monomer may be in the form of the free-acid oresterified derivatives thereof. Preferably, the dimethyl ester forms areused which have the following structures:

Isomeric arrangement of the carboxylate groups on the naphthalenesubstrate is an important consideration to the practice of thisinvention. High Tg polyester resins are readily obtained when each ofthe aromatic rings bears one of the carboxyl(ate) groups.

In one embodiment, the sulfopolyester contains repeat units from atleast two dicarboxylic acids, a diol, and a difunctional sulfomonomer.At least one of the dicarboxylic acids, component (a), is 10 to 93 molepercent based on 100 mole % dicarboxylic acid component, ofnaphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid,naphthalene-2,6-dicarboxylate ester, or naphthalene-2,7-dicarboxylateester. Preferably, the dimethyl ester forms are used.

In addition to the 2,6- or 2,7-naphthalene dicarboxylic acid or 2,6- or7-dicarboxylic ester, the dicarboxylic acid component contains 2 to 85mole percent of a dicarboxylic acid, component (b), which is selectedfrom aliphatic, alicyclic, and aromatic dicarboxylic acids. Examples ofthese dicarboxylic acids include malonic, dimethylmalonic, succinic,dodecanedioic, glutaric, adipic, trimethyladipic, pimelic,2,2-dimethylglutaric, azelaic, sebacic, fumaric, suberic, maleic,itaconic, 1,3-cyclopentane dicarboxylic, 1,2-cyclohexanedicarboxylic,1,3-cyclohexanedicarboxylic, 1,4-cyclohexanedicarboxylic, phthalic,terephthalic, isophthalic, 2,5-norbornanedicarboxylic, diphenic,4,4′-oxydibenzoic, diglycolic, thiodipropionic, 4,4′-sulfonyldibenzoic,1,8-naphthalenedicarboxylic, and 2,5-naphthalenedicarboxylic. Theanhydride, acid chloride, and ester derivatives of the above acids mayalso be used. The preferred dicarboxylic acid(s) to be used along withnaphthalene dicarboxylic acid or naphthalene dicarboxylate ester areisophthalic acid, terephthalic acid, dimethyl terephthalate, anddimethyl isophthalate.

One aspect of this invention concerns the amount of 2,6- or2,7-naphthalenediyl modification necessary for a given dicarboxylic acidor dicarboxylic acid combination to result in a polymer having a Tgabove 89° C. In general, the amount of 2,6- or 2,7-naphthalenediylmodification will decrease in the order:aliphatic>cycloaliphatic>aromatic. Increasing the chain length of analiphatic acid will result in a corresponding decrease in Tg, thus,requiring a higher level of naphthalenic modification.

The difunctional sulfomonomer component of the polyester may be adicarboxylic acid or an ester thereof containing a metal sulfonate group(—SO3-), a diol containing a metal sulfonate group, or a hydroxy acidcontaining a metal sulfonate group. Suitable metal cations of thesulfonate salt may be Na+, Li+, K+, Mg++, Ca++, Ni++, Fe++, Fe+++, Zn++and substituted ammonium. The term “substituted ammonium” refers toammonium substituted with an alkyl or hydroxy alkyl radical having 1 to4 carbon atoms. It is within the scope of this invention that thesulfonate salt is non-metallic and can be a nitrogenous base asdescribed in U.S. Pat. No. 4,304,901 which is attached hereto as ExhibitB.

The choice of cation will influence the water dispersibility of theresulting polyester. Monovalent alkali metal ions yield polyesters thatare less readily dissipated by cold water and more readily dissipated byhot water, while divalent and trivalent metal ions result in polyestersthat are not ordinarily easily dissipated by cold water but are morereadily dispersed in hot water. It is possible to prepare thesulfo-polyester using, for example, a sodium sulfonate salt and later byion-exchange replace this ion with a different ion, for example,calcium, and thus alter the characteristics of the polymer. In general,this procedure is superior to preparing the polymer with divalent saltsinasmuch as the sodium salts are usually more water soluble in thepolymer manufacturing components than are the divalent metal salts.Polymers containing divalent and trivalent metal ions are normally lesselastic and rubber-like than polymers containing monovalent ions.

Sulfopolyesters are more easily dispersed in water and/or form smalleraggregates in dispersion if the sulfopolyester has a high chargedensity. Cationic and anionic polymers are characterized by their chargedensity usually expressed in milliequivalents (meq) of anionic orcationic groups per gram of polymer. Charge densities of sulfopolyesterssuitable in this disclosure are in the approximate range of at leastapproximately 0.4 meq. and up to approximately to 0.9 meq/g.

The difunctional sulfomonomer contains at least one sulfonate groupattached to an aromatic nucleus wherein the functional groups arehydroxy, carboxy or amino. Advantageous difunctional sulfomonomercomponents are those wherein the sulfonate salt group is attached to anaromatic acid nucleus such as benzene, naphthalene, diphenyl,oxydiphenyl, sulfonyldiphenyl or methylenediphenyl nucleus. Examples ofsulfomonomers include sulfophthalic acid, sulfoterephthalic acid,sulfoisophthalic acid, 5-sodiosulfoisophthalic acid,4-sulfonaphthalene-2,7-dicarboxylic acid, and their esters.Metallosulfoaryl sulfonate which is described in U.S. Pat. No.3,779,993, which is attached hereto as Exhibit C, may also be used as asulfomonomer.

The sulfomonomer is present in an amount sufficient to provide waterdispersibility to the sulfo-polyester. Preferably, the sulfomonomer ispresent in an amount of from 15 to 40 mole percent, more preferably 15to 25 mole percent, based on the sum of the moles of total dicarboxylicacid content. In one example approximately 20 mole percent was foundsuitable.

The diol component of the polyester can be ethylene glycol, diethyleneglycol, propane-1,2-diol, 1,4-cyclohexanedimethanol or2,2-dimethyl-1,3-propanediol. The diol component may also includemixtures of the above diols. In addition, the diol component may includea sufficient amount of other cycloaliphatic or aromatic diols tosuitably increase the Tg of the polymer. Included within the class ofaliphatic diols are aliphatic diols having ether linkages such aspolydiols having 4 to 800 carbon atoms. Aromatic diols include bisphenolA (BpA) and/or other diphenylmethanederivatives and bisphenols with twohydroxyphenyl groups. Examples of additional diols are: diethyleneglycol, triethylene glycol, propane-1,3-diol, butane-1,4-diol,pentane-1,5-diol, hexane-1,6-diol, 3-methylpentanediol-(2,4),2-methylpentanediol-(1,4), 2,2,4-trimethylpentane-diol-(1,3),2-ethylhexanediol-(1,3), 2,2-diethylpropane-diol-(1,3),hexanediol-(1,3), 1,4-di-(hydroxyethoxy)-benzene,2,2-bis-(4-hydroxycyclohexyl)-propane,2,4-dihydroxy-1,1,3,3-tetramethyl-cyclobutane,2,2-bis-(3-hydroxyethoxyphenyl)-propane, and2,2-bis-(4-hydroxypropoxyphenyl)-propane. The diol component of thepolyester may also contain a diol selected from ethylene glycol,propane-1,2-diol, propane-1,3-diol, 1, 4-cyclohexanedimethanol and2,2-dimethyl-1,3-propanediol.

The particular combination of diols is stipulated only by therequirements that the final product possess a Tg equal to or greaterthan 45° C. while maintaining water dispersibility. Semi-crystalline andamorphous materials are within the scope of the present invention,although in most applications amorphous materials are contemplated. Itis to be understood that the sulfo-polyesters of this invention containsubstantially equal molar proportions of acid equivalents (100 mole %)to hydroxy equivalents (100 mole %). Thus, the sulfo-polyester comprisedof components (a), (b), and (c) will have a total of acid and hydroxylequivalents equal to 200 mole percent. The sulfo-polyesters have aninherent viscosity of 0.1 to 1.0 dl/g, preferably 0.2 to 0.6 dl/g.

A buffer may be added to the compositions of the present invention.Buffers and their use are well known in the art and do not requireextensive discussions. Suitable buffers include sodium acetate,potassium acetate, lithium acetate, sodium phosphate monobasic,potassium phosphate dibasic and sodium carbonate. The buffer is presentin an amount of up to 0.2 moles per mole of difunctional sulfomonomer.In one embodiment, the buffer is present in an amount of about 0.1 molesper mole of difunctional sulfomonomer.

An aspect of this disclosure concerns the effect of diol chain length onthe Tg of the resulting product. The structures: HO—(OCH2-CH2)n-OH andHO—CH2-(CH2)n-OH refer to the homologous series' of diols that arederived from ethylene and oxyethylene (i.e. diethylene) glycol. Valuesof n for the example based on ethylene glycol are normally in the rangefrom 1 to 12. As n increases the Tg for a resulting homopolyester resinis decreased accordingly. Therefore, modification of essentially asulfonate-containing poly(ethylene naphthalene dicarboxylate) requiresproportionately smaller molar amounts of codiol as n increases. Asimilar trend is observed when n increases from one (diethylene glycol)to about 10 for oxyethylene glycols.

In the case of high molecular weight oxyethylene glycol, also referredto as poly(ethylene glycol) or PEG, the value of n will be at least 10,preferably about 20, which translates into a PEG monomer molecularweight of at least 500, preferably around 1000. Typically less than 10mole percent of PEG incorporation, based on total diol, will be usedsince a Tg of greater than approximately 45° C. is required. Oneadvantage of high molecular weight PEG modification is the ability toattain higher molecular weights without losing water dispersibility. Itis important to note that high sulfomonomer levels result in highprocess melt viscosities which limit the molecular weight attainable inthe melt phase. A low molecular weight determined by an inherentviscosity measurement of less than 0.1 dl/g may result in poor physicalproperties such as low Tg and inadequate tensile strength.

The sulfo-polyesters can be prepared by conventional polycondensationprocedures well-known in the art. Such processes include directcondensation of the acid with the diol or by ester interchange usinglower alkyl esters. For example, a typical procedure consists of twostages. The first stage, known as ester-interchange or esterification,is conducted in an inert atmosphere at a temperature of 175° C. to 240°C. for 0.5 to 8 hours, preferably 1 to 4 hours. The diols, depending ontheir particular reactivities and the specific experimental conditionsemployed, are commonly used in molar excesses of 1.05 to 2.5 per mole ofnaphthalene dicarboxylate.

The second stage, referred to as polycondensation, is conducted underreduced pressure at a temperature of 230° C. to 350° C., preferably 265°C. to 325° C., and more preferably 270° C. to 290° C. for 0.1 to 6hours, preferably 0.25 to 2 hours. Because high melt viscosities areencountered in the polycondensation stage, it is sometimes advantageousto employ temperatures above 300° C. since the resulting decrease inmelt viscosity allows somewhat higher molecular weights to be obtained.Stirring or appropriate conditions are employed in both stages to ensuresufficient heat transfer and surface renewal for the reaction mixture.The reactions of both stages are facilitated by appropriate catalystswhich are well known in the art. Suitable catalysts include, but are notlimited to, alkoxy titanium compounds, alkali metal hydroxides andalcoholates, salts of organic carboxylic acids, alkyl tin compounds andmetal oxides.

Sulfo-Polyamides

The sulfo-polyamides of this disclosure are amorphous and dispersible inan aqueous solution. Amorphous (transparent) polyamides are described inU.S. Pat. Nos. 2,696,482 and 3,296,204, wherein each patent is herebyincorporated by reference in its entirety. The transparent nature of thepolyamide is obtained by using isophthalic acid (instead of terephthalicacid) as a reactant with a diamine to obtain the amorphous nature of thepolyamide.

One example of such a transparent sulfo-polyamide obtained bypolycondensation of bis-(4-amino cyclohexy)methane, at least onearomatic dicarboxylic acid and e-caprolactam, with a relative solutionviscosity of at least 1.5 consisting of (1) from to 35% by weight ofequimolar quantities of amino units (a) of the general formula and ofaromatic dicarboxylic acid units (b) of the general formula t 1 L 0 or 0and (2) from 30 to 65 by weight of lactam units (c) of the generalformula. Particularly preferred copolyamides according to the inventionare copolyamides consisting of from 60 to 70% by weight of equimolarquantities of units a) and of isophthalic acid units from 30 to 40% byweight of units (c).

In one embodiment, polyamides are prepared by employing as one of thereactants a sulfonated aromatic dicarboxylic acid. Suitable sulfonatedaromatic dicarboxylic acids include those having the structural formulas

In the above structural formulas M is an alkali metal such potassium,sodium lithium and cesium; A represents a direct bond or divalentradical selected from the group consisting of —O—, —CH2-CH2-,—O—CH2-CH2-O—, —SO2-, —CF2-, —C(CH3)2-,

And y and z are 0 or 1, the sum of y and z being at least 1.

It will be understood that, in the above structural formulas, any or allof the hydrogens in the carboxyl groups (—COOH) can be replaced withalkyl groups, usually the lower alkyl groups, and the —OH of the carboxygroups can be replaced by a halogen such as chlorine. Thus, thepolyamide: of this invention can be prepared by employing the loweralkyl esters and the acid chlorides of the above compounds.

The polyamides of this invention will contain in their molecular formularecurring structural units of the general structure

Wherein M, A, y and z are as previously defined.

In carrying out this invention the sulfonated aromatic dicarboxylic acidcan be employed in varying amounts. It has been determined, however,that amounts sufficient to provide a polyamide containing the aboverecurring structural units in amounts of from about 5 to 50 molepercent, with about 15 to 25 mole present being preferred, can beemployed. In general, the proportions of the respective recurring unitsin the polyamide will be found to be approximately the same as the moleproportions of the reactants.

Examples of sulfonated aromatic dicarboxylic acids that can be employedin carrying out this invention include the following:

The other reactants employed in this invention are well known polyamideforming compounds and include various amino acids having the generalformula

H2N—R—COOH

wherein R is selected from the group consisting of a divalent aliphaticradical, either straight or branched chain; a divalent alicyclicradical; and a divalent aromatic radical. If amino acids are employed,the polyamide will be comprised of, in addition to at least one of therecurring units I, II, and III, recurring units of the general structure

—HN—R1-CO—  IV

wherein R is as previously defined.

Also salts of various dicarboxylic acids and diamines represented by thestructural formulas

HOOC—R1-COOH

and

H2N—R2-NH2

can be employed in the preparation of the polyamides of this invention.In the above formulas R is selected from the group consisting ofdivalent aliphatic radicals, either straight or branched chain: divalentalicyclic radicals; and divalent non-sulfonated aromatic radicals. R2 isselected from the group consisting of divalent aliphatic radicals,either straight or branched chain; divalent alicyclic radicals; anddivalent aromatic radicals. Polyamides prepared from the above saltswill be comprised of, in addition to at least one of the structuralunits I, II, and III, recurring units of the general structure

—HN—R2-NH—CO—R1-CO—  V

wherein R and R are as above defined.

Instead of using the salt of the above defined diamines and dicarboxylicacids, the polyamides can be prepared by a condensation reaction from amixture of a diamine, as above defined, a dicarboxylic acid, as abovedefined, and a sulfonated aromatic dicarboxylic acid. Thus, for example,a mixture of the above compounds can be heated in a suitable reactionvessel, in an inert atmosphere, at a temperature of from about 200 C. to280 C. for about 2 to 4 hours, or longer depending on the viscositydesired of the resulting polyamide. The reaction can be convenientlycarried out in aqueous media or in a suitable solvent such as cresol,xylenol, o-hydroxydiphenyl. and the like. It is preferred, however, toemploy the salt of the diamine and dicarboxylic acid.

In a preferred method of preparing the polyamides a salt of thesulfonated aromatic dicarboxylic acid and a diamine is first prepared.Suitable diamines for this purpose include any of those set forthhereinabove for use in preparing salts of a diamine and the defineddicarboxylic acid. The salt can be conveniently produced by dissolvingsubstantially equimolar proportions of the diamine and the sulfonatedaromatic dicarboxylic acid in water and subsequently pouring thesolution into a nonsolvent for the formed salt, such as ethanol, whereinthe salt precipitates out.

The diamine-sulfonated aromatic dicarboxylic acid salt is then reactedwith (i) an amino acid, as above defined, or (2) a diamine-dicarboxylicacid salt, as above defined to produce the polyamides. Known polyamideforming methods can be employed. It is preferred, however, to prepare amixture of the above ingredients and heat the mixture in an inertatmosphere at a temperature of from about 230 C. to 260′ C. for about 1hour to 2 hours to form a low molecular weight polymer, a prepolymer.The reaction is carried out in aqueous media or in a solvent such ascresol, xylenol, or o-hydroxydiphenyl. The prepolymer is then heated andstirred, in its molten form, at a temperature of from about 240 C to 300C. for about 1 hour to 3 hours, or longer to produce a polyamide ofdesired viscosity. Alternatively, the prepolymer can be solidified andground to particle size, particles of a cross-sectional diameter ofabout 0.03 inch or smaller being satisfactory. The particles aresubsequently heated in a vacuum or in an inert atmosphere at 10 C. to 50C below their melting point for about 2 to 4 hours. Under theseconditions, the polymer can be built up to a relatively high viscosity.

Amino acids that can be used in carrying out this invention includestraight chain aliphatic amino acids having the structural formulawherein n represents an integer of 5 through 10 branched chain aliphaticamino acids of the same range of carbon atoms as the straight chainaliphatic amino acids, alicyclic amino acids, and aromatic amino acids.

Specific examples of amino acids include S-amino-n-valeric acid,G-amino-n-caproic acid, 7-amino-n-heptanoic acid, 1,2-amino-n-dodecanoicacid, 3-methyl-6-aminohexanoic acid, 4,4-dimethyl-7-aminoheptanoic acid4-ethyl-6-amino-hexanoic acid, 4-aminocyclohexanecarboxylic acid,3-aminomethylcyclohexanecarboxylic acid,4-aminoethylcyclohexanecarboxylic acid,4-aminomethylcyclohexanecarboxylic acid, 4-carboxypiperidine,∞-amino-p-toluic acid, ∞-amino-m-toluic acid,5-aminonorcamphane-2-carboxylic acid, and5-aminomethylnorcamphane-2-carboxylic acid.

As set forth hereinabove various salts of certain dicarboxylic acids anddiamines can be employed as one of the reactants in preparing thepolyamides.

Dicarboxylic acids suitable for this purpose include aliphaticdicarboxylic acids containing from 4 to 12 carbon atoms between thecarboxyl groups, either straight or branched chains, non-sulfonatedaromatic dicarboxylic acids, and alicyclic dicarboxylic acids.

Specific examples of aliphatic dicarboxylic acids include oxalic acid,dimethylmalonic acid, succinic acid, glutaric acid, adipic acid,2-methyladipic acid, 3-ethyladipic acid, pimelic acid, azelaic acid,suberic acid. sebacic acid, 3-ethylsebacic acid, and dodecanedioic acid.

Specific examples of alicyclic dicarboxylic acids include1,1-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid,1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid.The transisomer of the above acids is preferred; however, the cis isomeror mixtures of the two can be employed if desired. Other suitablealicyclic dicarboxylic acids include norcamphane-2,′5-dicarboxylic acid;norcamphane-2,6-dicarboxylic acid, and

Non-sulfonated aromatic dicarboxylic acids include phthalic acid.isophthalic acid, terephthalic acid, and the halogenated derivatives ofthese acids. Other suitable aromatic dicarboxylic acids include thoseacids having the structural formula

Wherein X can be, for example, a direct bond, —O—, —S—, —SO2-, —CH2-,—CH2-CH2, —CH2-CH2-CH2, —CH2-CH2-CH2-CH2-, —O—C2H4-O—, —C(CH3)2-,

Acids containing one or more ether groups in the molecular chain asrepresented by ethylenedioxydiacetic acid, 4,4′-oxydibutyric acid, and3,3′-oxydipropionic acid can be employed.

Suitable diamines for use in preparing the above-mentioned salt includealiphatic diamines containing 4 to 12 carbon atoms between the aminogroups, either straight or branched chains, alicyclic diamines, andamines containing one or more aromatic nuclei.

Specific examples of aliphatic diamines include ethylene diamine,tetramethylenediamine, pentamethylenediamine, hexamethylenediamine,octamethylenediamine, 1,12-diaminododecane,2,2-dimethyl-1.5-diaminopentane, 3,6-diethyl-1, 8-diaminooctane,2-methyl-1, 3-diaminopropane, 3-ethyl-1,6-diaminohexane, and4-butyl-1,10-decamethylenediamine. Diamines containing one or both aminogroups on a secondary carbon atom and diamines containing secondaryamino groups can also be employed.

Examples of specific alicyclic diamines include 1,2-diaminocyclohexane,1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1,1cyclohexanebis(methylamine), 1,2 cyclohexanebis(methylamine), 1,3cyclohexanebis (methylamine), and 1,4 cyclohexanebis(methylamine) Thesediamines can be used as the transisomer or use mixtures of cis andtrans-isomers. Other suitable alicyclic diamines include 2.5norcamphanediamine, 2.6 norcamphanediamine, 2,5norcamphanebis(methylamine), and 2,6-norcamphanebis(methylamine)

Diamines containing one or more aromatic nuclei include o-, m-, andp-xylene-∞,∞-diamines, and 3,4′-dl-(aminomethyl)diphenyl.

Diamines containing ether groups such, for example, as 3,3oxybis(propylamine), 3,3 (ethylenedioxy)bis (propylamine), and3,3′-(2,2-dimethyltrimethylenedioxy) bis(propylamine) can be employed.

It is understood that the polyamides herein can be prepared byemploying, in place of the above-defined acidic compounds, the loweralkyl esters thereof. The phenyl ester can also be employed if desired.Further, the acid chloride of the acidic compound can be employed inpreparing polyamides of this invention if desired. This is usuallyaccomplished in the presence of an acid-accepting agent.

In some instances it can be desirable to heat the sulfonated aromaticdicarboxylic acid with an excess of a diamine, usually about 25 molepercent to 45 mole percent, to provide a diamine that is terminated withamino groups. The dicarboxylic acid is then added in an amountmolecularly equivalent to the excess diamine employed and the reactionis completed as above described.

Sulfo-Polyurethanes

Sulfo-polyurethanes of this disclosure are produced by reacting anisocyanate containing two or more isocyanate groups per molecule(R—(N═C═O)_(n≥2)) with a polyol containing on average two or morehydroxy groups per molecule (R′—(OH)_(n≥2)), in the presence of acatalyst or by activation with ultraviolet light.

The properties of polyurethane may be greatly influenced by the types ofisocyanates and polyols used to make the polymer. In this disclosure,the polyurethane desired is a thermoplastic polyurethane (TPU), that isa polyurethane that has not been crosslinked. (although crosslinkedpolyurethanes have been contemplated). By thermoplastic is meant thatthe polyurethane does not soften or melt when heated. TPUs are typicallyformed by the reaction of (1) diisocyanates with short-chain diols(so-called chain extenders) and (2) diisocyanates with long-chain diols.The three reaction compounds allow for an enormous variety of differentTPUs.

Typically, polyurethanes have a rather low Tg such as below 50 C. Toincrease the Tg to one suitable for a water dispersible 3D printingmaterial for this disclosure, higher molecular weight molecules areadded to the polymer. Such molecules may be added via the diisocyanatereactant. Such molecules include cyclo aliphatic or aromatic components.Cycloaliphatic isocyanates, such as isophorone diisocyanate (IPDI) arebelieved to be suitable to raise the Tg to levels of 100 C or greater.Aromatic isocyanates such as diphenylmethane diisocyanate (MDI) ortoluene diisocyanate (TDI) are also believed to be suitable. Althoughspecific aliphatic and aromatic diisocyanates have been mentionedherein, it is contemplated that other diisocyanates may also be used forthe purposes described herein.

The 5-sodiosulfoisophthalic acid (5-SSIPA) component is introduced byconversion of the acid component to an isocyanate or to a diolcomponent. If converted to a diol component, the sodium salt can besubstituted for the polyol needed to produce the polyurethane.

Alternatively a polyol component can be used having higher moleculargroups such as the cycloaliphatics or aromatics discussed above and thesodiumsulfoisophthalic isocyanate may be directly used in the productionreaction to produce the polyurethane.

The following examples are included for illustrative purposes only andare not intended to limit the scope of this disclosure.

Examples

The table set forth below associated polymers with a particular Tg, usedto make parts, with water dispersible polymer types or combinations madeunder this disclosure having compatible Tgs.

Part Material/Non-Water dispersible Polymers Glass TransitionTemperature (Tg) ° C. Polylactic acid 48 Acrylonitrile Butadiene Styrene#1 123 #2 120 Polycarbonate #1 155 #2 155 Ultem 9085; polymer from 185Stratasys Ltd. of Eden Prairie, MN, USA Ultem 1010; polymer from 225Stratasys Ltd. of Eden Prairie, MN, USA Support Structure Waterdispersible Polymer Compositions tested, having Compatible Tgs, %Monomers Polyester Polyester Polyester Polyester Polyester PolyamidePolyamide Composition One: Ethylene glycol 100 100 100 100 CompositionTwo: Diethylene glycol 75 1,4-Cyclohexyldimethanol 25 Composition ThreeVariations: Dimethyl napthalene 60 60 50 60 dicarboxylic acid Adipicacid 5 Succinic acid 10 10 5 Dimethyl 5- 35 30 40 35sodiosulphoisophthalic acid Composition Four Variations:5-sodiosulphoisophthalic acid 24 30 Terephthalic acid 35 Isophthalicacid 76 35 Composition Five: Hexamethyldiamine 100 Composition Six:4,4′-methylenebis(2- 36 methylcyclohexylamine) Laurolactam 28Isophthalic acid 6 5-sodiosulphoisophthalic acid 30

1. A water dispersible sulfo-polymer configured for use as a consumablefeedstock in the additive manufacture of a part comprising a non waterdispersible polymer, wherein the water dispersible sulfo-polymer is areaction product of a sulfo monomer and the reaction product is at leaston selected from the group consisting of a sulfo-polyamide, asulfo-polyesteramide, and a sulfo-polyurethane with approximately 18 to35% sulfoisophthalic monomer, the water dispersible sulfo-polymer beingdispersible in water resulting in separation of the water dispersiblepolymer from the three-dimensional part comprising the non waterdispersible polymer. 2-3. (canceled)
 4. The water dispersible polymer ofclaim 1 comprising the reaction product of a condensation reaction. 5-6.(canceled)
 7. The water dispersible polymer of claim 1 comprisingapproximately 20 to 35% sulfoisophthalic monomer.
 8. The waterdispersible polymer of claim 1 comprising approximately 25 to 35%sulfoisophthalic monomer.
 9. The water dispersible polymer of claim 3wherein the water dispersible polymer is characterized by a glasstransition temperature of at least approximately 45 C.
 10. The waterdispersible polymer of claim 1 wherein the water dispersible polymer issubstantially amorphous.
 11. The water dispersible polymer of claim 1wherein the water dispersible polymer is at least semi-crystalline. 12.The water dispersible polymer of claim 1 wherein the water dispersiblepolymer has a charge density of at least about 0.4 meq./g, suitable toexhibit water solubility or water dispersibility without the aid of anyother solubility or dispersibility adjuvant.
 13. The water dispersiblepolymer of claim 1 wherein a sulfonated aromatic diacid or diol monomeris used in the synthesis thereof. 14-20. (canceled)
 21. A waterdispersible sulfo polymer configured for use as a consumable material inthe additive manufacture of a part comprising: a non water dispersiblepolymer, wherein the water dispersible polymer is a reaction product ofa metal sulfo monomer selected from the group consisting of asulfo-polyamide, a sulfo-polyesteramide, and a sulfo-polyurethane withapproximately 18 to 35% sulfoisophthalic monomer, the water dispersiblesulfopolymer being dispersible in water resulting in separation of thewater dispersible polymer from the part comprising the non waterdispersible polymer.
 22. The water dispersible sulfopolymer of claim 21comprising the reaction product of a condensation reaction.
 23. Thewater dispersible sulfo polymer of claim 21 comprising approximately 20to 35% sulfoisophthalic monomer.
 24. The water dispersible sulfo polymerof claim 21 comprising approximately 25 to 35% sulfoisophthalic monomer.25. The water dispersible sulfo polymer of claim 21 wherein the waterdispersible sulfo polymer is characterized by a glass transitiontemperature of at least approximately 45 C.
 26. The water dispersiblesulfo polymer of claim 21 wherein the water dispersible polymer issubstantially amorphous.
 27. The water dispersible sulfo polymer ofclaim 21 wherein the water dispersible polymer is at leastsemi-crystalline.
 28. The water dispersible sulfo polymer of claim 21wherein the water dispersible polymer has a charge density of at leastabout 0.4 meq./g, suitable to exhibit water solubility or waterdispersibility without the aid of any other solubility or dispersibilityadjuvant.
 29. A consumable feedstock material for use in an additivemanufacturing system, the consumable feedstock material comprising: awater dispersible sulfo polymer comprising a reaction product of asulfur monomer and the reaction product is at least one selected fromthe group consisting of a sulfo-polyamide, a sulfo-polyesteramide, and asulfo-polyurethane with approximately 18 to 35% sulfoisophthalicmonomer.
 30. The consumable feedstock material of claim 29, wherein thereaction product includes or approximately 20 to 35% sulfoisophthalicmonomer.
 31. The consumable feedstock material of claim 29, wherein thereaction product includes or approximately 25 to 35% sulfoisophthalicmonomer.
 32. The consumable feedstock material of claim 29, wherein thewater dispersible sulfo polymer is characterized by a glass transitiontemperature of at least approximately 45 C.
 33. The consumable feedstockmaterial of claim 29, wherein the water dispersible sulfo polymer issubstantially amorphous.
 34. The consumable feedstock material of claim29, wherein the water dispersible polymer is at least semi-crystalline.35. The consumable feedstock material of claim 29, wherein the waterdispersible sulfo polymer has a charge density of at least about 0.4meq./g.
 36. The consumable feedstock material of claim 29, wherein thewater dispersible sulfo polymer has a charge density of between about0.4 meq/g and about 0.9 meq./g.
 37. The consumable feed stock materialof claim 29, wherein the feedstock is in a filament form.
 38. Theconsumable feed stock material of claim 29, wherein the feedstock is ina powder form.